If you develop a listeria infection, you may experience:

• Fever
• Muscle aches
• Nausea
• Diarrhea

Symptoms may begin a few days after you've eaten contaminated food, but it may take as long as two months before the first signs and symptoms of infection begin.

If the listeria infection spreads to your nervous system, signs and symptoms may include:

• Headache
• Stiff neck
• Confusion or changes in alertness
• Loss of balance
• Convulsions

Symptoms during pregnancy, for newborns
During pregnancy, a listeria infection is likely to cause only mild signs and symptoms in the mother. The consequences for the baby, however, may be devastating. The baby may die unexpectedly before birth or experience a life-threatening infection within the first few days after birth.

As in adults, the signs and symptoms of a listeria infection in a newborn can be subtle, but may include:

• Little interest in feeding
• Irritability
• Fever
• Vomiting

When to see a doctor
If you've eaten a food that's been recalled because of a listeria outbreak, pay close attention to any possible signs or symptoms of illness. If you experience fever, muscle aches, nausea or diarrhea, contact your doctor. The same goes for illness after eating a potentially contaminated product, such as foods made with unpasteurized milk or poorly heated hot dogs or deli meats.

If you experience a high fever, severe headache, confusion, a stiff neck or sensitivity to light, seek emergency care. These signs and symptoms may indicate bacterial meningitis, a life-threatening complication of a listeria infection.

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Listeria infections are caused by eating food contaminated with the bacteria Listeria monocytogenes, which can be found in:

• Soil
• Water
• Some wild and domestic animals

Humans are often exposed to listeria by consuming:

• Raw vegetables that have been contaminated from the soil or from contaminated manure used as fertilizer
• Infected animal meat
• Unpasteurized milk or foods made with unpasteurized milk
• Certain processed foods — such as soft cheeses, hot dogs and deli meats that have been contaminated after processing

Unborn babies can contract a listeria infection from the mother via the placenta. Breast-feeding is not considered a potential cause of infection.

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Those at highest risk of a listeria infection include:

• Pregnant women and their babies. Pregnant women are significantly more susceptible to listeria infections than are other healthy adults. In fact, nearly one-third of listeria infections occur during pregnancy, according to the CDC. Although a listeria infection may cause only a mild illness in the mother, consequences for the baby may include miscarriage, stillbirth, premature birth or a potentially fatal infection after birth.
• People who have weak immune systems. This includes older adults and anyone who has AIDS, cancer, diabetes, kidney disease or other conditions that affect the immune system, as well as those who take medications to block rejection of a transplanted organ.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Most listeria infections are so mild they may go unnoticed. However, in some cases, a listeria infection can lead to life-threatening complications — including:

• A generalized blood infection (septicemia)
• Inflammation of the membranes and fluid surrounding the brain (meningitis)

Complications of a listeria infection may be most severe for an unborn baby. Early in pregnancy, a listeria infection may lead to miscarriage. Later in pregnancy, a listeria infection may lead to stillbirth, premature birth or a potentially fatal infection in the baby after birth — even if the mother becomes only mildly ill.

Infants who survive a listeria infection may experience long-term neurological damage and delayed development.

Adults over 60 can also be seriously affected by a listeria infection, and death rates may be as high as 10 to 20 percent for this age group.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

You're likely to start by first seeing your family doctor, general practitioner or if you're pregnant, your obstetrician. However, you may then be referred to a doctor who specializes in infectious diseases.

Here's some information to help you get ready for your appointment, as well as what information your doctor might want from you.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Try to construct a food diary, going back as far as you can reliably remember.
• Make a list of medications, vitamins and supplements that you're taking.
• Write down questions to ask your doctor.

Preparing a list of questions ahead of time can help you make the most of your time together. List your questions from most important to least important in case time runs out. For listeria, some basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• Could anything else cause these symptoms?
• What kinds of tests do I need?
• What treatments are available, and which do you recommend?
• What types of side effects can I expect from treatment?
• I'm pregnant. What effect will this have on my baby?
• Are there any brochures or other printed materials that I can take home with me? What Web sites do you recommend visiting?

In addition to the questions that you've prepared, don't hesitate to ask questions during your appointment any time you don't understand something.

What to expect from your doctor
Your doctor is likely to ask you a number of questions to aid in the diagnosis. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

• When did you first begin experiencing symptoms?
• Have you eaten any soft cheeses, such as Brie, Camembert, feta, queso blanco or queso fresco recently? Or raw milk or cheese made from raw milk? What about processed meats, such as cold cuts or hot dogs?
• Have you consumed any foods that have been implicated in a recent food recall?
• How severe are your symptoms?
• Do you have any conditions or take any medications that affect your immune system?

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

A blood test is often the most effective way to determine whether you have a listeria infection. In some cases, samples of spinal fluid, urine or the fluid that surrounds and protects a baby before birth (amniotic fluid) may be tested as well.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

A listeria infection is treated with intravenous antibiotics in the hospital. The sooner treatment begins, the better. During pregnancy, prompt antibiotic treatment may help keep the infection from affecting the baby. Newborns who have a listeria infection may receive a combination of antibiotics.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

To prevent a listeria infection, follow simple food safety guidelines:

• Wash your hands, utensils and food surfaces often. To prevent cross-contamination — the transfer of harmful bacteria from one surface to another — wash your hands thoroughly with warm, soapy water before and after handling or preparing food, especially raw meat, poultry, fish, shellfish and eggs. After cooking, use hot, soapy water to wash the utensils, cutting board and other food preparation surfaces.
• Separate raw foods from ready-to-eat foods. When shopping, separate meat and poultry products from the rest of your groceries. At home, tightly wrap raw meat packages in plastic bags to prevent leaking juices from contaminating other food. Use separate cutting boards for raw meat and ready-to-eat foods, such as bread and vegetables. Use separate plates for raw meat and cooked meat.
• Wash raw vegetables thoroughly before eating. Clean raw vegetables with a scrub brush or vegetable brush under plenty of running water.
• Cook your food thoroughly. Use a food thermometer to make sure your meat, poultry and egg dishes are cooked to a safe temperature.
• Refrigerate or freeze perishable foods promptly. Harmful bacteria can reproduce rapidly if foods aren't properly cooled. Set your refrigerator to 40 F (4 C) or cooler. When shopping, select perishable food last to minimize time away from the refrigerator or freezer.
• Avoid unpasteurized milk and milk products. Don't drink raw milk or eat any products made with unpasteurized milk.

Precautions for people particularly at risk
If you're at risk of a listeria infection — you're pregnant or you have a weak immune system — you may want to be particularly cautious about listeria. Take additional precautions with these types of foods:

• Soft cheeses and Mexican-style cheeses. Don't eat soft cheeses such as feta, Brie, Camembert, blue cheese, and Mexican-style cheeses such as queso blanco and queso fresco, unless it's clear from the packaging that the product was made using pasteurized milk.
• Hot dogs, luncheon meats and deli meats. Avoid hot dogs, luncheon meats and deli meats, unless they're reheated until steaming hot. Keep fluid from hot dog packages away from other foods, utensils and food preparation surfaces. Wash your hands after handling hot dogs, luncheon meats or deli meats.
• Meat spreads. Don't eat refrigerated pates or meat spreads. Canned or shelf-stable pates and meat spreads are acceptable.
• Refrigerated smoked seafood. Don't eat refrigerated smoked seafood. Such products may be labeled as nova-style, lox, kippered or jerky. One exception is if you're using these products in a casserole or other cooked dish. Canned or shelf-stable smoked seafood is acceptable.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.